Before boarding old vessel in gorge (7)
I believe the answer is:
overeat
'gorge' is the definition.
('overeat' can be a synonym of 'gorge')
'before boarding old vessel' is the wordplay.
'before' becomes 'ere' (usually literary).
'boarding' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'vessel' becomes 'vat' (vat is a kind of vessel**).
'o'+'vat'='ovat'
'ere' put within 'ovat' is 'OVEREAT'.
'in' acts as a link.
(Other definitions for overeat that I've seen before include "Be gluttonous" , "Indulge in gluttony" , "ignore threat of a big corporation?" , "Gorge oneself" , "Consume too much like a glutton" .)